Combination of SEC-MALS and Fluorescence with Molecular Dynamics Simulations for the Analysis of Ionomer Dimensions in Solution. Application to Poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co<

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• 作者：Gema Marcelo ; Francisco Mendicuti ; Enrique Saiz ; M. Pilar Tarazona
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：February 20, 2007
• 年：2007
• 卷：40
• 期：4
• 页码：1311 - 1320
• 全文大小：452K
• 年卷期：v.40,no.4(February 20, 2007)
• ISSN：1520-5835

文摘

Solution properties of an ionomer, poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-styrene)(PAMPST) with a 95 mol % styrene content, are investigated by using size exclusion chromatography (SEC)coupled with differential refractive index (RI) and multiangle light scattering (MALS) detectors and steady-statefluorescence measurements. Dimensions of ionomers in solution depend on the polarity of the solvent that modifiesthe interactions of the ionic groups. Measurements were performed in two solvents of very different dielectricconstant, namely tetrahydrofuran (THF) and dimethylformamide (DMF), and the addition of a low molecularweight electrolyte such as LiCl to both solvents clearly improves the results affording scaling laws and unperturbeddimensions. In spite of the different thermodynamic quality of the solvents DMF and THF solutions, theextrapolations to unperturbed dimensions provide similar values of the characteristic ratio C_n = 11-12. Howeverexcimer-to-monomer emission intensity ratios, as consequence of the different origin of excimers, substantiallydepend on the solvent THF/DMF composition. Molecular dynamics simulations performed on oligomers ofPAMPST in THF, THF + LiCl, DMF, and DMF + LiCl solvents support the conclusions obtained fromexperimental measurements.